1. Field of the Invention
The present invention relates to a flip chip package with a heat sink and manufacturing method thereof. More particularly, the present invention relates to a flip chip package that uses underfill material to firmly fasten a substrate and a heat sink within the package and the manufacturing method thereof.
Description of the Related Art
Flip chip interconnect technology is a method of bonding a chip to a substrate as well as connecting the two electrically. To form a flip chip package, a chip with an array of bonding pads formed on an active surface is provided. Bumps are formed over the bonding pads. Thereafter, the chip is flipped over such that the contacts on a substrate are aligned with the respective bumps on the chip. Thus, the substrate and the chip are electrically and mechanically connected via the bumps so that the chip is able to communicate with an external device through the internal circuits inside the substrate.
It is known that the flip chip technology is capable of producing a chip package having a high pin count while reducing overall package area and shortening overall signal transmission pathways at the same time. Consequently, flip chip technique has been widely adopted in the fabrication of many types of chip packages. The most common type of flip chip package structure includes the so-called “flip chip ball grid array” (FC/BGA), for example. However, as the operational speed of the chip is increased, more efficient heat-dissipating device must be accompanied.
To increase heat-dissipating efficiency, a heat sink is frequently attached to the backside of a FC/BGA package. In the conventional technique, a reflow process is carried out after a chip is flipped over (the active surface facing downward) and aligned on top of a substrate so that the bumps on the surface of the chip re-melt and bond with corresponding contacts on the substrate. Because the substrate and the chip have widely different coefficient of thermal expansion, considerably stress may build up between the chip and the bumps under thermo cycles. Ultimately, the chip may crack or else the package may warp noticeably.